Coupled inductor filter with frequency notching characteristics for grid interface

A novel design of a power grid interface using a coupled inductor filter with a frequency notching characteristic is presented in this paper. Traditional grid-tie power converters are connected to the supply grid via an L filter, an LC filter or an LCL filter, respectively, to reduce the harmonics caused by the switching. The efficiency of the grid interface can be improved by reducing the switching frequency and the size of the filtering inductor. To reduce the size of the filtering inductor and retaining the similar attenuation characteristics for the switching ripples, a coupled inductor filter is used to replace the conventional filter. To illustrate the capability of the proposed approach, the design of a coupled inductor notch filter to attenuate the switching ripples is provided. A simple controller has also been derived for the grid interface to act as an active power filter such that a power factor correction and a harmonics reduction can both be achieved. The proposed coupled inductor filter could be applied to any applications requiring a power grid interface. The experimental results are included to demonstrate the effectiveness of the proposed filter.